Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with a graphical user interface in accordance to my new design.

The even broken line showing of the graphical user interface of a poker table and the dash-dot broken line showing of the display screen are provided for purposes of illustrating portions of the article and form no part of the claimed design. 

CLAIM The ornamental design for a for a display screen or portion thereof with a graphical user interface, as shown and described. 